17. What are the safety management objectives for a shipping company? ① provide for sea practices in ship operation and a safe working environment ② establish safeguards against all identified risks ③ continuously improve safety-management skills of personnel ashore and aboard of ships ④ make the comfortable implements for the rest of seafarers. (A) ①②③ (B) ②③④ (C) ①③④ (D) ①②④